Genes of the most conserved WOX clade in plants affect root and flower development in Arabidopsis.
BACKGROUND
The Wuschel related homeobox (WOX) family proteins are key regulators implicated in the determination of cell fate in plants by preventing cell differentiation. A recent WOX phylogeny, based on WOX homeodomains, showed that all of the Physcomitrella patens and Selaginella moellendorffii WOX proteins clustered into a single orthologous group. We hypothesized that members of this group might preferentially share a significant part of their function in phylogenetically distant organisms. Hence, we first validated the limits of the WOX13 orthologous group (WOX13 OG) using the occurrence of other clade specific signatures and conserved intron insertion sites. Secondly, a functional analysis using expression data and mutants was undertaken.


RESULTS
The WOX13 OG contained the most conserved plant WOX proteins including the only WOX detected in the highly proliferating basal unicellular and photosynthetic organism Ostreococcus tauri. A large expansion of the WOX family was observed after the separation of mosses from other land plants and before monocots and dicots have arisen. In Arabidopsis thaliana, AtWOX13 was dynamically expressed during primary and lateral root initiation and development, in gynoecium and during embryo development. AtWOX13 appeared to affect the floral transition. An intriguing clade, represented by the functional AtWOX14 gene inside the WOX13 OG, was only found in the Brassicaceae. Compared to AtWOX13, the gene expression profile of AtWOX14 was restricted to the early stages of lateral root formation and specific to developing anthers. A mutational insertion upstream of the AtWOX14 homeodomain sequence led to abnormal root development, a delay in the floral transition and premature anther differentiation.


CONCLUSIONS
Our data provide evidence in favor of the WOX13 OG as the clade containing the most conserved WOX genes and established a functional link to organ initiation and development in Arabidopsis, most likely by preventing premature differentiation. The future use of Ostreococcus tauri and Physcomitrella patens as biological models should allow us to obtain a better insight into the functional importance of WOX13 OG genes.
Deveaux
Yves
Y
Université Paris-Sud 11, Institut de Biotechnologie des Plantes, Bâtiment 630, UMR/CNRS 8618, F-91405 Orsay, France. yves.deveaux@u-psud.fr
Toffano-Nioche
Claire
C
Claisse
Gaelle
G
Thareau
Vincent
V
Morin
Halima
H
Laufs
Patrick
P
Moreau
Hervé
H
Kreis
Martin
M
Lecharny
Alain
A
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics*; D017124:Conserved Sequence; D056890:Eukaryota / Q000235:genetics / Q000502:physiology; D035264:Flowers / Q000254:growth & development* / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D023061:Gene Order; D018745:Genome, Plant / Q000235:genetics; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism; D010944:Plants / Q000145:classification / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics
D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C116421:WUSCHEL protein, Arabidopsis